Clinical features and therapeutic implications of 104 episodes of monomicrobial Aeromonas bacteraemia

OBJECTIVES

Aeromonas bacteraemia is not a common infectious disease, but can cause a grave outcome in infected cases. In this study, clinical presentations and prognostic factors of cases of monomicrobial Aeromonas bacteraemia were analysed. Also, the impact of beta-lactam and aminoglycoside in combination and of emerging cephalosporin-resistance during therapy was discussed.

METHODS

From 1989 to 1998 in a medical centre in southern Taiwan, those cases with monomicrobial Aeromonas bacteraemia were included for study.

RESULTS

A total of 104 episodes of monomicrobial Aeromonas bacteraemia, accounting for 74% of all Aeromonas bacteraemia, were encountered. The infections usually occurred in the patients with hepatic cirrhosis (54%) or malignancy (21%) and were community-acquired (74%). Cases of community-acquired bacteraemia were more likely to have cirrhosis, a high severity score at onset, and a worse prognosis than those of nosocomial bacteraemia did and nosocomial isolates were less susceptible to cefoxitin and cefotaxime. Forty-three percent of cases had a concomitant infection focus, such as primary peritonitis, invasive cellulitis or necrotizing fasciitis, biliary tract or burn wound infections. Crude fatality rate within 2 weeks after the onset was 30%. Secondary bacteraemia and a higher severity score ( > or = 4) for illness at the first presentation were independently associated with a fatal outcome. The therapeutic superiority of beta-lactam and aminoglycoside in combination cannot be demonstrated in patients with Aeromonas bacteraemia. Cefotaxime resistance emerged in 3.4% of 58 patients treated with a cephalosporin for at least 72 h. None of the community-acquired isolates, but one-quarter of the nosocomial isolates, were resistant to cefotaxime.

CONCLUSIONS

Aeromonas bacteraemia usually occurred in patients with liver cirrhosis or malignancy, and heralded a poor prognosis, especially while associated with a relevant infectious source or with a higher severity score at presentation. The superiority of aminoglycoside and beta-lactam in combination cannot be demonstrated while treating those patients, and the emergence of antimicrobial resistance to cephalosporin was a rare event during cephalosporin therapy. Thus, a broad-spectrum cephalosporin remains one of the antimicrobial alternatives for invasive community-acquired Aeromonas infections.

Demonstration of a conserved histidine and two water ligands at the Mn2+ site in Diocleinae lectins by pulsed EPR spectroscopy

Lectins from the Diocleinae subtribe, including Canavalia brasiliensis, Canavalia bonariensis, Canavalia grandiflora, Cratylia floribunda, Dioclea grandiflora, Dioclea guianensis, Dioclea rostrata, Dioclea violacea, and Dioclea virgata, have been recently isolated and characterized in terms of their carbohydrate binding specificities. Although all of the lectins are Man/Glc specific, they possess different biological activities. In the present study, electron paramagnetic resonance (EPR) spectroscopy demonstrates that all nine Diocleinae lectins contain Mn2+. The spectra of C. floribunda and D. rostrata suggest Mn2+ site symmetry different from that of the other seven lectins. However, electron spin-echo envelope modulation (ESEEM) spectroscopy indicates that all nine lectins are coordinated to a histidyl imidazole, with similar electron-nuclear coupling to the Mn2+-bound imidazole nitrogen. ESEEM also demonstrates ligation of two water molecules to Mn2+ in all nine Diocleinae lectins. Thus, the EPR and ESEEM data indicate the presence of a Mn2+ binding site in the above Diocleinae lectins with a conserved histidine residue and two water ligands.

Pilonidal disease in Singapore: clinical features and management

BACKGROUND

Pilonidal disease has not been well documented in Asian people. The aims of the present study were to investigate any variations in the clinical features and effectiveness of various surgical treatments in such a population.

METHODS

A prospectively collected computerized database of 61 consecutive patients admitted to a specialist colorectal unit over a 9-year period was studied. The five methods of surgical treatment used during this period (incision and drainage; laying open; marsupialization; primary closure; and the flap procedure) were compared.

RESULTS

There were 38 men and 23 women with a mean age of 27+/-1.02 years. Pilonidal disease was significantly more common among the Indian people (52.5% of patients) than the other ethnic races in the Singaporean community (P < 0.001). Chronic discharging sinuses were the most common presentation (93.4%). There were no differences between the various surgical techniques employed with regard to the time required for wound healing (mean: 48+/-21 days) and recurrence rates (4/61, 6.6%). Wound dehiscence after primary wound closure (10%) and flap procedures (42%) meant that the overall healing rate was not faster than when the wound was just laid open. Furthermore, flap procedures required a longer hospitalization than other procedures (P = 0.005).

CONCLUSION

Pilonidal disease was more common among Indian people, the more hirsute among the Singaporean population. Primary closure and flap procedure did not improve overall wound healing because of dehiscence.

Dilatation of the biliary tree in children: sonographic diagnosis and its clinical significance

We evaluated sonographically 162 children who met the criteria for biliary tract dilatation in the past 18 years. Of these, 131 patients were diagnosed as having anomalous dilatations of the biliary tree (including 112 with choledochal cysts and 19 with biliary duct dilatation and biliary atresia). Biliary tract dilatations in the other 31 patients were due to secondary causes or normal variants. All cases of intrahepatic biliary tree dilatation and those with both intra- and extrabiliary duct dilatations were anomalous. In 117 cases of extrahepatic biliary tract dilatation only, the mean diameter was widest in cases of choledochal cyst (21.4 +/- 12.1 mm, compared with cases of biliary tract dilatation with biliary atresia (10 +/- 2.4 mm), secondary biliary duct dilatation (8.5 +/- 1.5 mm), and normal variants (4.4 +/- 1.2 mm) (P < 0.001). Of the 43 infants with biliary tree dilatation, 24 (56%) had choledochal cysts and 19 (44%) had biliary tract dilatation associated with biliary atresia. Excluding cases associated with biliary atresia, the accuracy of diagnosing choledochal cysts in extrahepatic biliary tract dilatation was 71% and 97% using cutoffs of 7 mm and 10 mm as the minimum diameter, respectively.

Spectroscopic properties of fluoroquinolone antibiotics and nanosecond solvation dynamics in aerosol-OT reverse micelles

Among fluoroquinolone antibiotics, ofloxacin (OFL) and norfloxacin (NOR) have piperazinyl groups but flumequine (FLU) does not have this substitutent. The emission spectra of OFL and NOR are strong, broad structureless bands with large Stokes' shifts in water but the emission intensities are very weak in organic solvents. Thus we find that these compounds exist as different chemical species in various solvents. A continuous red shift in the emission bands for OFL and NOR is observed as the water concentration within the aerosol-OT (AOT; sodium 1,4-bis[2-ethylhexyl]sulfosuccinate) micelle increases or temperature of this solution rises. From the fluorescence anisotropy measurements of OFL and NOR, we assume the intramolecular charge transfer after excitation from the nitrogen of the piperazinyl group to the keto oxygen. Theoretical calculations further support this observation. Multifrequency phase and modulation experiments and time-resolved emission spectra clearly show the occurrence of intramolecular charge transfer and the subsequent nanosecond water reorganization around OFL or NOR in the AOT micelle. Upon increasing the water concentration within the AOT micelle, the relaxation rate increases because of the large amount of free water. The emission spectra of FLU do not exhibit any significant response to the physical properties of their environment.

Segmental dilatation of the ileum as an unusual cause of gastrointestinal bleeding: report of one case

We report a case of segmental dilatation of the ileum in a 10-month-old male infant. Intermittent loose black-colored stool passage and normocytic anemia were noted at the initial visits to our hospital. There was no symptom or sign of intestinal obstruction such as abdominal distention or vomiting. On physical examination, he was found to be pale but his abdomen was soft and flat. Digital examination revealed brownish stool tinged with black-colored oil-like stool but no polyp. Laboratory studies excluded coagulopathy, hemolytic anemia and lead poisoning. During hospitalization, he was treated with nothing per mouth, intravascular fluids, ranitidine, and transfusion of packed red blood cells. All examinations including panendoscopy, Technetium-99m (99mTc)-pertechnetate Meckel's diverticulum scan, and double contrast colon series revealed no organic lesion except that 99mTc-red blood cell bleeding scans showed abnormal bleeding in the small intestine. Because of his persistent gastrointestinal bleeding with unknown cause, we did an exploratory laparotomy when the patient was 13 months old and idiopathic segmental dilatation of the ileum was confirmed. The dilated segment is supposed to be idiopathic because of histologically proven normal muscle layers without ectopic tissue. This case suggests that segmental dilatation of the ileum can only present as gastrointestinal bleeding without intestinal obstruction.

Effects of cyclosporin A on sex hormone and estrogen receptor in male rat with special reference to cyclosporin A-induced osteoporosis

The mechanisms of high turnover bone loss induced by Cyclosporin A (CsA) are not clearly understood. Deficiencies in sex hormones result in high turnover osteoporosis, and not only androgen but also estrogen plays an important role in maintaining bone mass in men. To study whether or not there are any changes in the levels of sex hormones, aromatization, and the expression of estrogen receptors in CsA-induced osteoporosis, we treated 39 rats with vehicle, low-dose CsA (5 mg/kg) and high dose CsA (15 mg/kg) for 28 days, and measured sex hormone levels by radioimmunoassay. Aromatase activities in ROS cells and 3T3-L1 cells were determined by measuring the conversion rate of 3H-androstenedione into 3H-estrone. ER and ER mRNA were measured by competitive RT-PCR in collected marrow cells and ROS cells. The levels of free testosterone in the serum in low-dose CsA-treated rats were unchanged, but the levels were significantly decreased in those treated with high-dose CsA as previously reported. The levels of total estradiol in the serum were significantly increased in the low-dose CsA-treated group (5 mg/kg) and were comparable to levels of the control group in the high-dose CsA-treated group (15 mg/kg). CsA increased the conversion of 3H-androstenedione to 3H-estrone in ROS cells, but not in 3T3-L1 cells. Meanwhile, CsA treatment did not change the rates of ER or ER mRNA expression in ROS cells or in collected bone marrow cells. In conclusion, CsA treatment decreased the level of free testosterone in the serum, but did not decrease the level of serum estradiol by enhancing aromatization. High-turnover osteoporosis induced by clinical dosage CsA treatment may not be caused by lowering the levels of circulating estrogen or by decreasing the expression of estrogen receptors.

Origin of the native driving force for protein folding

We derive an expression with four adjustable parameters that reproduces well the 20x20 Miyazawa-Jernigan potential matrix extracted from known protein structures. The numerical values of the parameters can be approximately computed from the surface tension of water, water-screened dipole interactions between residues and water and among residues, and average exposures of residues in folded proteins.

Mean-field HP model, designability and alpha-helices in protein structures

Analysis of the geometric properties of a mean-field HP model on a square lattice for protein structure shows that structures with a large number of switchbacks between surface and core sites are chosen favorably by peptides as unique ground states. Global comparison of model (binary) peptide sequences with concatenated (binary) protein sequences listed in the Protein Data Bank and the Dali Domain Dictionary indicates that the highest correlation occurs between model peptides choosing the favored structures and those portions of protein sequences containing alpha helices.

Possibility of wound dressing using poly(L-leucine)/poly(ethylene glycol)/poly(L-leucine) triblock copolymer

ABA-type block copolymers (abbreviated as LEL) composed of poly(L-leucine) (PLL) as the A component and poly(ethylene glycol) (PEG) as the B component were synthesized by ring-opening polymerization of L-leucine N-carboxyanhydride initiated by primary amino group located at both ends of PEG chain. A silver sulfadiazine (AgSD)-impregnated wound dressing of sponge type was prepared by the lyophilization method. Morphological structure of this wound dressing by scanning electron microscopy was observed to be composed of a dense skin layer and a porous inner layer. Equilibrium water content of LEL wound dressing increased with an increase in PEG content in the block copolymer due to the hydrophilicity of PEG. AgSD release from AgSD-impregnated wound dressing in PBS buffer (pH = 7.4) was dependent on PEG content in the block copolymer. Release of AgSD was increased in proportion to the PEG content in the copolymer. Antibacterial capacity of AgSD-impregnated wound dressing was examined in agar plate against Pseudomonas aeruginosa and Staphylococcus aureus. It was found that the suppression of bacterial proliferation in the wound dressing was dependent upon the PEG content. In cytotoxicity test, cell damage did not occur by the release of AgSD from the LEL sponge matrix of AgSD-medicated wound dressing. In in vivo test, granulous tissue formation and wound contraction for the AgSD- and dehydroepiandrosterone-impregnated LEL-2 wound dressing were faster than for any other groups.

NAADP: An emerging calcium signaling molecule

Cells possess multiple Ca(2+) stores and multiple messengers for mobilizing them. In addition to inositol trisphosphate and cyclic ADP-ribose, nicotinic acid adenine dinucleotide phosphate (NAADP), a metabolite of NADP, is shown to be a potent Ca(2+) signaling molecule in both invertebrate and mammalian cells. This article summarizes the recent results of this newly discovered Ca(2+) signaling mechanism and explores the implications of the apparent proliferation of Ca(2+) messengers.

Phenotypic heterogeneity in a Chinese family with mitochondrial disease and A3243G mutation of mitochondrial DNA

The A3243G mutation of mitochondrial DNA (mtDNA) has been shown to be responsible for or associated with mitochondrial myopathy, encephalopathy, lactic acidosis, strokelike episodes (MELAS) syndrome, diabetes mellitus (DM) and several other neuromuscular diseases. We used polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) to identify the A3243G mtDNA mutation and an electron microscope to examine mitochondrial derangement in the muscle biopsies of a 38-year-old man suspected to have MELAS syndrome with DM. We found great variability in the clinical presentation and in the proportion of mtDNA with the A3243G mutation in the matrilineal family members of the patient. The proband had atypical MELAS syndrome, recurrent vascular headache, and DM (MELASDM), and his mother manifested chronic progressive ptosis and DM (CPPDM). Brain magnetic resonance imaging of the proband showed high signal intensity in the left temporoparieto-occipital area on T2 weighted images (T2WI). The blood lactate level ranged from 2.32 to 4.70 mmol/l, and two-hour postprandial glucose ranged from 124 mg/dl to 148 mg/dl. The blood lactate and postprandial glucose of the proband's mother were 3.15 mmol/l and 192 mg/dl, respectively. Electron microscopic examination of a muscle biopsy of the patient showed abnormal mitochondria with decreased density of cristae and membrane degeneration. No ragged-red fibers were detected in muscle upon staining with modified Gomori trichrome. The hair follicles and blood cells of the patient and his mother showed the A3243G mutation in the tRNA(Leu)(UUR) gene. The proportions of the mutant DNA in the hair follicles and blood cells of the proband were 36.8% and 35.2%, respectively, and those of the patient's mother were 28.8% and 13.9%, respectively. We conclude that the A3243G mtDNA mutation may manifest with MELASDM or CPPDM in different matrilineal members of the same family as a result of differences in random segregation of the heteroplasmic A3243G mutant mtDNA in the affected tissues of patients.

Synthesis, radiolabeling, and biodistribution of putative metabolites of iodoazomycin arabinoside

Scintigraphic evaluation of patients with advanced oncological disease showed uptake of radioactivity in the brain following administration of the hypoxic imaging agent 123I-iodoazomycin arabinoside (123I-IAZA). Three proposed metabolites of IAZA--methyl 5-deoxy-5-iodo-D-arabinofuranoside, methyl 2,3-di-O-acetyl-5-deoxy-5-iodo-alpha-D-arabinofuranoside, and 1-(5-deoxy-5-iodo-alpha-D-arabinofuranosyl)-2-aminoimidazole (IAIA)--were synthesized, radiolabeled with 125I, and investigated in normal and tumor-bearing murine models for their contribution to this unusual phenomenon. The three compounds were readily radiolabeled by melt or solvent exchange procedures. Biodistribution data indicated rapid blood clearance, rapid excretion, and little tissue accumulation in the brain. IAIA showed significant tumor to blood ratios at 4 h (4.3:1) and liver to blood ratios at 24 h (30:1).

Absence of maternal A3243G mtDNA mutation and reversible hyperglycemia in a patient with MELAS syndrome

We report the unusual features of a female patient who had MELAS-specific A3243G mutation in mitochondrial DNA (mtDNA) and diabetes mellitus (DM). The patient showed mitochondrial myopathy, encephalopathy, lactic acidosis, and deafness but lacked the stroke-like episode. Acute hyperglycemia was noted after one attack of status epilepticus. Molecular genetic analysis demonstrated a heteroplasmic A3243G point mutation in the mtDNAs of muscle, blood cells and hair follicles. Glucagon stimulation test exhibited marked depression of pancreatic beta-cell function. However, in a further study neither this mutation, nor MELAS syndrome or DM, was found in all of her maternal relatives. A series of follow-up studies for beta-cell function also showed gradual improvement. The pedigree study led us to believe that this A3243G mutation arose from the germ line cells or occurred later in somatic tissues of the patient. We also suggest that the A3243G mutation of mtDNA may elicit the pathogenesis of a subtype of DM. Nevertheless, environmental stress may be another important factor for provocation of the disease.

Mitochondrial role in life and death of the cell

Mitochondria are the major ATP producer of the mammalian cell. Moreover, mitochondria are also the main intracellular source and target of reactive oxygen species (ROS) that are continually generated as by-products of aerobic metabolism in human cells. A low level of ROS generated from the respiratory chain was recently proposed to take part in the signaling from mitochondria to the nucleus. Several structural characteristics of mitochondria and the mitochondrial genome enable them to sense and respond to extracellular and intracellular signals or stresses in order to sustain the life of the cell. It has been established that mitochondrial respiratory function declines with age, and that defects in the respiratory chain increase the production of ROS and free radicals in mitochondria. Within a certain concentration range, ROS may induce stress responses of the cell by altering the expression of a number of genes in order to uphold energy metabolism to rescue the cell. However, beyond this threshold, ROS may elicit apoptosis by induction of mitochondrial membrane permeability transition and release of cytochrome c. Intensive research in the past few years has established that mitochondria play a pivotal role in the early phase of apoptosis in mammalian cells. In this article, the role of mitochondria in the determination of life and death of the cell is reviewed on the basis of recent findings gathered from this and other laboratories.

Mitochondrial role in life and death of the cell

Mitochondria are the major ATP producer of the mammalian cell. Moreover, mitochondria are also the main intracellular source and target of reactive oxygen species (ROS) that are continually generated as by-products of aerobic metabolism in human cells. A low level of ROS generated from the respiratory chain was recently proposed to take part in the signaling from mitochondria to the nucleus. Several structural characteristics of mitochondria and the mitochondrial genome enable them to sense and respond to extracellular and intracellular signals or stresses in order to sustain the life of the cell. It has been established that mitochondrial respiratory function declines with age, and that defects in the respiratory chain increase the production of ROS and free radicals in mitochondria. Within a certain concentration range, ROS may induce stress responses of the cell by altering the expression of a number of genes in order to uphold energy metabolism to rescue the cell. However, beyond this threshold, ROS may elicit apoptosis by induction of mitochondrial membrane permeability transition and release of cytochrome c. Intensive research in the past few years has established that mitochondria play a pivotal role in the early phase of apoptosis in mammalian cells. In this article, the role of mitochondria in the determination of life and death of the cell is reviewed on the basis of recent findings gathered from this and other laboratories.

Reduced erythropoietin responsiveness to anemia in diabetic patients before advanced diabetic nephropathy

We often encounter diabetic patients with anemia in whom the causes of anemia were not clearly identified despite differential hematologic studies. We therefore studied the clinical and biochemical characteristics of diabetic patients with anemia of uncertain cause and measured erythropoietin (Epo) concentrations in 35 diabetic subjects without significant diabetic renal disease. Among 62 medical records of diabetic patients with anemia, showing no evidence of advanced diabetic nephropathy (creatinine clearance > or = 30 mg/kg/1.73 m2), the causes of the anemia were not able to be identified in 28 cases (45.2%). In addition, we enrolled 35 diabetic patients with uncertain causes of anemia in order to evaluate the serum Epo responsiveness to anemia, and compared levels to a group of non-diabetic subjects also with anemia. The serum Epo concentrations of diabetic patients (17.6 +/- 8.1 mIU/ml) were significantly lower than those of non-diabetic patients with similar degree of decrease in hemoglobin concentrations (144.9 +/- 108.0 mIU/ml, P<0.001). The hemoglobin concentrations of diabetic patients correlated with creatinine clearance (r = 0.34, P = 0.03), serum creatinine (r = -0.49, P = 0.003) and albumin excretion rate (r = -0.44, P = 0.009), but showed no relation to age, duration of diabetes, glycated hemoglobin, presence of retinopathy or neuropathy. We concluded that reduced Epo responsiveness to anemia could explain the anemia present in diabetic patient but without advanced diabetic nephropathy. This may reflect early renal interstitial damage.

Cyclic 3-deaza-adenosine diphosphoribose: a potent and stable analog of cyclic ADP-ribose

Cyclic 3-deaza-adenosine diphosphoribose (3-deaza-cADPR), an analog of cyclic adenosine diphosphoribose (cADPR) was synthesized. 3-deaza-cADPR differs from cADPR by only the substitution of carbon for nitrogen at the 3-position of the purine ring. Similar to cADPR, the analog has potent calcium releasing activity in sea urchin egg homogenates and was able to induce calcium release at concentrations as low as 0.3 nM. The EC(50) value for 3-deaza-cADPR-induced calcium release was 1 nM, which is about 70 times more potent than cADPR. The properties of calcium release induced by 3-deaza-cADPR in all other respects were similar to those of cADPR. Thus, 3-deaza-cADPR and cADPR were capable of cross-desensitizing each other and their calcium releasing activities were potentiated by Sr(2+) as well as caffeine. 8-amino-cADPR, a selective antagonist of cADPR, was also able to inhibit 3-deaza-cADPR induced calcium release. Taken together, these data suggest that 3-deaza-cADPR releases calcium through the same mechanism as cADPR. 3-deaza-cADPR was found to be resistant to both heat and enzymatic hydrolysis. Only 15% of 3-deaza-cADPR was destroyed after boiling this compound for 2 h. No loss of 3-deaza-cADPR was observed when treated with CD38 under conditions where cADPR was completely hydrolyzed. Thus, 3-deaza-cADPR is a potent and stable analog of cADPR. These properties should make 3-deaza-cADPR a useful probe in studies focused on the mechanism of cADPR action.

Identification of the ligands to the ferric heme of Chlamydomonas chloroplast hemoglobin: evidence for ligation of tyrosine-63 (B10) to the heme

We have studied the unusual heme ligand structure of the ferric forms of a recombinant Chlamydomonas chloroplast hemoglobin and its several single-amino acid mutants by EPR, optical absorbance, and resonance Raman spectroscopy. The helical positions of glutamine-84, tyrosine-63, and lysine-87 are suggested to correspond to E7, B10, and E10, respectively, in the distal heme pocket on the basis of amino acid sequence comparison of mammalian globins. The protein undergoes a transition with a pK of 6.3 from a six-coordinate high-spin aquomet form at acidic pH to a six-coordinate low-spin form. The EPR signal of the low-spin form for the wild-type protein is absent for the Tyr63Leu mutant, suggesting that the B10 tyrosine in the wild-type protein ligates to the heme as tyrosinate. For the Tyr63Leu mutant, a new low-spin signal resembling that of alkaline cytochrome c (a His-heme-Lys species) is resolved, suggesting that the E10 lysine now coordinates to the heme. In the wild-type protein, the oxygen of the tyrosine-63 side chain is likely to share a proton with the side chain of lysine-87, suggested by the observation of a H/D sensitive resonance Raman line at 502 cm(-)(1) that is tentatively assigned as a vibrational mode of the Fe-O bond between the iron and the tyrosinate. We propose that the transition from the high-spin to the low-spin form of the protein occurs by deprotonation and ligation to the heme of the B10 tyrosine oxygen, facilitated by strong interaction with the E10 lysine side chain.

Oxidative stress is insignificant in N1S1-transplanted hepatoma despite markedly declined activities of the antioxidant enzymes

It has been proposed that persistent oxidative stress accounts for the increased levels of DNA damage in cancer tissues. We have examined the profile of anti-oxidant enzymes in a transplanted hepatic tumor model by injecting N1S1 rat hepatoma cells into the liver of Sprague-Dawley rats. The transplanted N1S1 tumors displayed characteristics resembling human hepatocellular carcinoma. The immunoreactivities of catalase (CAT), manganese-superoxide dismutase (Mn SOD), copper/zinc-SOD (Cu/Zn SOD), and glutathione peroxidase (GPx) were found to decrease significantly. The enzyme activity in tumors decreased 26.2-, 4.2-, 4.5-, and 5.4-fold for CAT, Mn SOD, Cu/Zn SOD, and GPx, respectively, relative to those in normal liver tissue from the same animals. In contrast, the mRNA levels of CAT and GPx in tumors decreased only 5- and 2-fold, respectively, and the mRNA levels of Cu/Zn SOD and Mn SOD showed either no change or an increase as compared to those of normal liver tissue. The contents of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) and thiobarbituric acid-reactive substances (TBARS) were comparable to those of normal controls. Furthermore, mitochondrial production of superoxide in tumors was 4 times lower than that in normal tissues. In conclusion, the data indicate that the reduced activities of anti-oxidant enzymes in the N1S1 tumor did not cause significant oxidative stress.

A systematic analysis of secondary DNA transfer

The Nature letter by R. van Oorschot and M. Jones (1) addressed two topics: the primary transfer of DNA from person to person or to various objects, and the secondary transfer of DNA through an intermediary. Forensic scientists have described the primary transfer of DNA and other biological evidence for many years. However, the authors also reported detecting secondary transfer of DNA from an object to a person's hands, which could adversely affect DNA typing in the forensic context. The prospect of secondary transfer raises questions of interest to both the legal and forensic communities. Therefore, we sought to evaluate parameters potentially leading to secondary DNA transfer. Our data do not support the conclusion that secondary transfer will compromise DNA typing results under typical forensic conditions.

Characterization of group D1 non-typhoid Salmonella isolates by serotyping and pulsed field gel electrophoresis

Non-typhoid salmonella infection is not uncommon in immunocompetent patients in Taiwan. Bacterial factors may play an important role in the pathogenesis of such infections. In a previous study, Salmonella group D1 was found to have the tendency to cause bacteremia with a higher frequency than other serotypes. In the present study, we prospectively collected 94 Salmonella group D1 isolates for serotyping and molecular typing. Salmonella panama and Salmonella dublin seemed more invasive than other serotypes. Pulsed field gel electrophoresis was also done to characterize of Salmonella enteritidis and Salmonella dublin. PFGE type "a" of Salmonella dublin appeared to be more invasive than the other two PFGE types. All six Salmonella dublin isolates were Vi antigen negative. Further study using a larger number of isolates is needed to identify the tendency to invade blood stream of Salmonella dublin and Salmonella panama.

Error mode prediction

The study of accidents ('human errors') has been dominated by efforts to develop 'error' taxonomies and 'error' models that enable the retrospective identification of likely causes. In the field of Human Reliability Analysis (HRA) there is, however, a significant practical need for methods that can predict the occurrence of erroneous actions--qualitatively and quantitatively. The present experiment tested an approach for qualitative performance prediction based on the Cognitive Reliability and Error Analysis Method (CREAM). Predictions of possible erroneous actions were made for operators using different types of alarm systems. The data were collected as part of a large-scale experiment using professional nuclear power plant operators in a full scope simulator. The analysis showed that the predictions were correct in more than 70% of the cases, and also that the coverage of the predictions depended critically on the comprehensiveness of the preceding task analysis.